The present invention relates generally to conveyor systems and, more particularly, to a side flexing modular link conveyor system having improved construction and operating characteristics.
Conveyor systems are an integral part of modern production facilities. Such systems are especially beneficial in the food processing and article packaging industries, where it is often desirable to move articles to and from different areas of the production facility to undergo various manufacturing/packaging operations. Due to constraints, such as limitations in floor space, it is often necessary to provide bends or curves in the conveyor system to move articles in a desired direction for positioning at a specific location.
A significant problem encountered with present day modular link conveyor belts is concerned with the substantial increase in the drag force in curves as the linear speed of the conveyor increases. Specifically, the inner side links of the belt are compressed upon entering the curve and the outside links are expanded. These competing forces place the conveyor belt in lateral tension along the radius of the curve. This tension, in turn, causes the outer links to press against the outer guide rail, which is usually simply a curved, stainless steel channel. It is known that this contact creates the deleterious xe2x80x9chot spotsxe2x80x9d as the frictional drag force on the conveyor belt escalates. Left unchecked, the frictionally generated heat eventually causes the plastic depending arm of the side link to soften, which can lead to failure.
Even if the speed is reduced sufficiently to avoid failure, the frictional drag force reduces the operating efficiency of the system itself, since more power is required to overcome this force. Even if the heat rise is controlled, the side links of the conveyor belt wear more rapidly, which further increases the incidence of link or belt failure. These difficulties inevitably lead to costly production downtime.
Conventional attempts to reduce the troublesome drag force have met with little success. For instance, it is well-known that providing a constant source of lubrication to the curved guide rails can temporarily reduce friction and the resulting drag force. However, for many production operations, such as food processing, the presence of industrial lubricants presents a significant problem, as the food product is subject to contamination. The lubricants readily trap loose food product and, thus, create an unsanitary residue which provides a breeding ground for bacteria or the like. Furthermore, because of the requirement for frequent washing to meet governmental regulations, even if the lubricant is ruled safe to be around the food product, the cost of frequent reapplication to the rails is prohibitive.
One early proposal for overcoming the above mentioned problems associated with drag force is taught in U.S. Pat. No. 3,094,206 to Stewart. This reference discloses a flexible wire conveyor belt having a pair of centrally-located depending legs with shoulders which track along a series of rollers secured near the center of the conveyor frame. While this proposal seeks to reduce the drag force by substituting rollers for the conventional passive or static guide rail, it is apparent that such a design lacks the stability that is required in modem operations, especially during high speed belt operation. Specifically, the presence of a single guide rail in the center fails to consistently maintain the belt flat, thus leaving the belt edges free to flex upwardly and away from the conveyor support frame.
Modem efforts to improve the tribological characteristics in modular-type conveyors have moved away from the teaching of the ""206 patent and have instead sought to alleviate the problem by redesigning the conveyor belt itself. Most, if not all, of such proposals involve the attachment of rollers directly to the underside of the belt to reduce the drag force. During operation, these rollers track along one or more passive guide rails in an attempt to guide the belt along the curve with less friction. For example, U.S. Pat. No. 5,573,105 to Palmaer discloses a modular link conveyor belt having a plurality of rollers carried under the belt. These rollers also engage a center rail. A similar example of such a design is U.S. Pat. No. 5,038,925 to Chrysler, which teaches the use of a conveyor belt having split rollers mounted along its peripheral edge for engaging a passive guide rail.
While these proposals are improvements over conventional approaches, such as the concept of applying a lubricant, several limitations still remain. The complexity and expense of the conveyor belt is the main drawback, since the cost of construction more than doubles. Furthermore, with the number of rollers increasing by ten/twenty fold or more, the chances of failure leading to downtime are greatly increased. Also, from a sanitary viewpoint, these extra rollers increase the problem of cleaning the belt to meet the governmental standards.
Still others propose external modifications to the conveyor belt. For example, in U.S. Pat. No. 3,946,857 to Fraioli, Sr., a series of rollers are mounted along the periphery of the conveyor belt for tracking along a passive guide rail. However, it is readily apparent from viewing this proposed design that similar limitations remain; namely, complexity and cost of design, increasing incidence of belt failure, and complicating the cleaning process.
In addition to negotiating curves, it is often beneficial to provide the conveyor belt with up/down ramping capabilities. This added dimension of travel not only provides significant flexibility in moving articles to and from production areas, such as where the work stations have different height requirements, but also where there are different levels of the production facility itself.
Thus, a need exists for a side flexing, modular conveyor system with improved operating characteristics. Such an improved system would be simple in design, inexpensive to construct and maintain, and would include the ability to smoothly and efficiently negotiate horizontal curves or bends by substantially reducing the troublesome drag force associated with passive guide rails. Additionally, the belt would be provided with an improved ability to ramp up and down smoothly and reliably. Further, the improved system and its conveyor belt would travel more efficiently along the return run.
Thus, it is one object of the present invention to provide a side flexing modular link conveyor system having an improved construction and tribological characteristics that overcome the above described limitations and disadvantages of the prior art conveyor systems.
An additional object of the invention is to provide such a conveyor system having an active guide rail that significantly reduces the frictional drag on the conveyor belt as it negotiates a curve, thereby providing smooth and efficient operation.
Still another object is to provide such a conveyor system having an active guide rail that is selectively adjustable for use in a variety of curves.
Yet another object is to provide such a conveyor system with a side flexing modular link conveyor belt having improved side links that engage a series of roller assemblies in an advantageous manner along one or both edges of the conveyor to enhance the speed of operation.
Still a further object is to provide such a side flexing, modular link conveyor belt having improved side links that also allow the belt to ramp up and down more efficiently, and also to assist in supporting the belt along the return run.
Additional objects, advantages and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention as described herein, a conveyor system having an improved design exhibiting enhanced tribological characteristics is provided. As a result, the system achieves a more efficient motion of the side flexing, modular link conveyor belt that forms a component of the system. The improved operation, and the resultant longer life, comes primarily as a result of reducing the frictional drag force around curves of the conveyor. An improvement to the conveyor belt itself and the side links are also features of the present invention.
Generally, a modular link conveyor belt is formed by interconnecting a plurality of modular links. A complete description of this type of belt, and an associated conveyor system, is disclosed in Applicant""s U.S. Pat. No. 4,953,693 to Draebel, entitled, xe2x80x9cModular Link Conveyor System.xe2x80x9d The disclosure of this patent is incorporated herein by reference.
In accordance with an important aspect of the present invention, the improved conveyor system includes at least one active guide rail with one or more roller assemblies for guiding a modular link conveyor belt. This guide rail is positioned along either the inside or the outside of any curved section of the conveyor system. Although providing an active guide rail along both the inside and outside curve is contemplated, the preferred embodiment is directed to guiding along the outside rail. It should be appreciated that where only one active guide rail is present, the other may be a passive guide rail of a type known in the art. A description of such a passive guide rail in the form of an outwardly directed channel is found in Applicant""s ""693 patent, noted above. Also, in one alternate embodiment, a single active guide rail may be provided for supporting both sides of the conveyor belt.
Preferably, each roller assembly comprises an upper roller for directing the upper or production run of the belt and a lower roller for the return run. Each roller is rotatably mounted on a spindle and has a circumferential groove that defines a pair of spaced disks. The periphery of each disk provides a bearing surface that rolls substantially friction free over an inner guide surface of the vertically depending portion of each link. More specifically, the inside facing surfaces of the groove slidingly engage and capture the top and bottom surfaces of the inwardly projecting tab of the side link. As can be appreciated, the upper roller of each assembly thus serves to actively guide the conveyor belt with minimum frictional drag force as it travels on the forward or production run, while the lower roller serves to similarly guide and support the belt along the return run. Advantageously, the active rotation of the rollers serves to reduce the frictional drag force exerted on the conveyor belt, whereby the allowable speed of travel can be significantly increased. The belt traverses a curve or bend in the conveyor system without being subject to excessive wear. The generation of frictional heat is also greatly reduced at any point in the system.
In the preferred embodiment, a plurality of such roller assemblies are interconnected to form the active guide rail. Specifically, a pair of articulated members are coupled together between adjacent roller assemblies using the spindles as the coupler. The articulated members are preferably attached to the spindle in a pivotal relationship, which allows the relative angular position between the roller assemblies to be selectively adjusted. This feature enhances flexibility, since the plurality of roller assemblies and, more particularly, the active guide rail, can be selectively adjusted to adapt to a variety of different curved sections of conveyor.
Additionally, the improved conveyor system includes one or more radial cross brackets, preferably fabricated of rigid sheet metal or the like, for supporting the active guide rail. These cross brackets extend between the inside and outside guide rails, whether both active or active/passive. If desired, the brackets can be adapted to allow for the adjustment of the relative position of the guide rails. Support for the conveyor system itself is provided by any means well known in the art, such as upstanding legs that connect to the frame.
According to a second aspect of the present invention, an improved side link is provided for assisting in guiding and supporting the conveyor belt. In the preferred embodiment, the depending arm portion of each side link is provided with a curved skirt. The curved skirt includes a forwardly projecting fin and a rearwardly projecting fin. The side links form the outer edges of the conveyor belt and interconnect with modular links to provide a conveying surface.
In operation, the forwardly projecting fin of a trailing link overlaps in close proximity with the rearwardly extending fin of a leading link at any moment in time. As can be appreciated, the overlapping of these fins forms a curved juncture that serves to bridge the gap between the consecutive side links. This overlapping function provides the conveyor belt with several enhanced operational capabilities.
First of all, the curved skirt assists in allowing the conveyor belt to smoothly traverse a bend or curve. Specifically, at the curved juncture between the fins, the roller remains in contact with the skirt of the leading link as contact is initially made with the trailing link. This improves stability and reduces the vibration experienced by the belt as the curve is traversed. Secondly, the edges of the fins of adjacent links are also allowed to contact each other. This advantageously provides cooperative edge-to-edge support in the event temporary sagging of the belt occurs. In this way, any tendency of the belt to disconnect from the guide rail is avoided.
The inter-engaging fins of consecutive side links also provide improved ramping capabilities. Preferably, as the belt ramps up an incline, the forwardly projecting fin of the trailing link rotates in a backward fashion such that it mates with the rearwardly projecting fin of the leading link. This edge-to-edge engagement advantageously serves to support and guide each successive link during such a ramping operation. A similar benefit is provided when the belt is ramping down a decline.
Additionally, the edge-to-edge engagement provided by the cooperating curved skirts advantageously improves operation during the return run. As the belt is inverted, the rearwardly projecting fin of the skirt of the leading link at any moment in time can be supported on the forwardly projecting fin of the trailing link. This assures that any tendency of the individual links to sag as they traverse between the roller assemblies of the active guide rail is corrected.
In accordance with a third aspect of the invention, an active guide rail is provided that is comprised of at least one roller assembly. As described above, this roller assembly includes upper and lower rollers for directing the corresponding upper (production) or lower (return) run of the belt. Each roller is coaxially and rotatably mounted on an upstanding spindle. As the belt traverses along the guide rail, the periphery of each roller provides a bearing surface that simultaneously rolls substantially friction free over the inner guide surfaces of the vertically depending arm portion of each link on both side edges of the belt. As can be appreciated, the upper roller of each assembly thus serves to actively guide the conveyor belt with minimum frictional drag force as it travels on the forward or production run, while the lower roller serves to similarly guide and support the belt along the return run.
In a most preferred embodiment, the individual rollers have a circumferential groove that defines a pair of spaced disks, and each side of the belt is provided with a specialized side or guide link having an inwardly projecting transverse tab for engaging this groove. More specifically, the inside facing surfaces of this groove slidingly engage the top and bottom surfaces of the inwardly projecting tab of the side link at one side of the belt along both the upper and lower runs, while a similar engagement is provided for the projecting tab at the opposite side of the belt. Since each link is thus captured in this embodiment, any tendency for lifting is eliminated, yet the desirable reduced friction rolling contact is still afforded.
As in the preferred embodiment, a plurality of roller assemblies are interconnected in a single row to form the active guide rail in this alternate embodiment. Specifically, a pair of articulated members are coupled together between adjacent pairs of roller assemblies using the spindles as the coupler. Since the articulated members are attached to the spindle in a pivotal relationship, the relative angular position between the roller assemblies can be selectively adjusted. This advantageously allows the plurality of roller assemblies and, more particularly, the active guide rail, to adapt to a variety of different curved sections of conveyor. Since only a single active guide rail is provided, a freestanding support may be used to support the active guide rail as an alternative to radial cross brackets.
Still other objects of the present invention will become apparent to those skilled in this art from the following description wherein preferred and alternate embodiments of this invention are shown, simply by way of illustration of one of the modes best suited to carry out the invention. As it will be realized, the invention is capable of other different embodiments and its several details are capable of modification in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.